Synthesis gas production system and method

ABSTRACT

A synthesis gas production system (302) incudes a gas turbine (310) having a compressor (312) with an autothermal reformer (308) between the compressor (312) and the turbine (314). The system (302) may include a separator (326) for removing a portion of the mass exiting the compressor (312) prior to its delivery to the autothermal reformer (308). Gaseous light hydrocarbons are delivered to the autothermal reformer (308) through conduit (330) and may be selectively controlled with a valve (331). Synthesis gas production system (302) may be used with a methanol process, ammonia process, a Fischer-Tropsch process (304), or other process involving synthesis gas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.08/879,553, filed Jun. 20, 1997 (Abandoned), by Kenneth L. Agee, Mark A.Agee, Larry J. Weick and Elliot L. Trepper and entitled "SYSTEM ANDMETHOD FOR CONVERTING LIGHT HYDROCARBONS TO HEAVIER HYDROCARBONS", asamended.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/020,092, filed Jun. 21, 1996.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a system and method for convertinglight hydrocarbons into heavier hydrocarbons and more particularly to aconversion system having a combined autothermal reformer and turbine.

BACKGROUND OF THE INVENTION

Synthesis gas, or "syngas," is a mixture of gases prepared as feedstockfor a chemical reaction; for example, carbon monoxide and hydrogen tomake hydrocarbons or organic chemicals, or hydrogen and nitrogen to makeammonia. Syngas may be produced for use with a Fischer-Tropsch process,which is described further below and which is used as an examplethroughout.

The synthetic production of hydrocarbons by the catalytic reaction ofcarbon monoxide and hydrogen is known and is generally referred to asthe Fischer-Tropsch reaction. Numerous catalysts have been used incarrying out the reaction, and at relatively low to medium pressure(near atmospheric to 600 psig) and temperatures in the range of fromabout 300° F. to 600° F., both saturated and unsaturated hydrocarbonscan be produced. The synthesis reaction is very exothermic andtemperature sensitive whereby temperature control is required tomaintain a desired hydrocarbon product selectivity. The Fischer-Tropschreaction can be characterized by the following general reaction:

    2H.sub.2 +CO→.sub.Catalyst -CH.sub.2.sup.- +H.sub.2 O

Two basic methods have been employed for producing the synthesis gasutilized as feedstock in the Fischer-Tropsch reaction. The two methodsare steam reforming, wherein one or more light hydrocarbons such asmethane are reacted with steam over a catalyst to form carbon monoxideand hydrogen, and partial oxidation, wherein one or more lighthydrocarbons are combusted or reacted sub-stoichiometrically to producesynthesis gas.

The basic steam reforming reaction of methane is represented by thefollowing formula:

    CH.sub.4 +H.sub.2 O.sub.Catalyst →CO+3H.sub.2

The steam reforming reaction is endothermic and a catalyst containingnickel is often utilized. The hydrogen to carbon monoxide ratio of thesynthesis gas produced by steam reforming of methane is approximately3:1.

Partial oxidation is the non-catalytic, sub-stoichiometric combustion oflight hydrocarbons such as methane to produce the synthesis gas. Thebasic reaction is represented as follows:

    CH.sub.4 +1/2O.sub.2 →CO+2H.sub.2

The partial oxidation reaction is typically carried out using highpurity oxygen. High purity oxygen can be quite expensive. The hydrogento carbon monoxide ratio of synthesis gas produced by the partialoxidation of methane is approximately 2:1.

In some situations these approaches may be combined. A combination ofpartial oxidation and steam reforming, known as autothermal reforming,wherein air is used as a source of oxygen for the partial oxidationreaction has also been used for producing synthesis gas heretofore. Forexample, U.S. Pat. Nos. 2,552,308 and 2,686,195 disclose low pressurehydrocarbon synthesis processes wherein autothermal reforming with airis utilized to produce synthesis gas for the Fischer-Tropsch reaction.Autothermal reforming is a combination of partial oxidation and steamreforming where the exothermic heat of the partial oxidation suppliesthe necessary heat for the endothermic steam reforming reaction. Theautothermal reforming process can be carried out in a relativelyinexpensive refractory lined carbon steel vessel whereby low cost istypically involved.

The autothermal process results in a lower hydrogen to carbon monoxideratio in the synthesis gas than does steam reforming alone. That is, asstated above, the steam reforming reaction with methane results in aratio of about 3:1 while the partial oxidation of methane results in aratio of about 2:1. The optimum ratio for the hydrocarbon synthesisreaction carried out at low or medium pressure over a cobalt catalyst is2:1. When the feed to the autothermal reforming process is a mixture oflight hydrocarbons such as a natural gas stream, some form of additionalcontrol is desired to maintain the ratio of hydrogen to carbon monoxidein the synthesis gas at the optimum ratio of about 2:1.

In producing a product from the synthesis unit, a residue gas isfrequently produced. For some processes, the use of this gas to createenergy has been suggested. Systems that have utilized the residue gashave required numerous additional components and steps to do so.

In producing a synthesis gas for the Fischer-Tropsch process or anyother process, it is desirable to produce the synthesis gas asefficiently as possible. The ability to develop a process with lowcapital expense may be an imperative to development of large-scalesystems.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for a synthesis gas production system thataddresses the shortcomings of the prior art. According to an aspect ofthe present invention, a synthesis gas production system includes a gasturbine with an autothermal reformer (ATR) interposed between thecompressor and expander and wherein the ATR produces syngas and servesas the combustor for the gas turbine.

According to another aspect of the present invention, a system forconverting lighter hydrocarbons to heavier hydrocarbons includes: asynthesis gas production unit having a compressor, an autothermalreformer fluidly coupled to the compressor for producing synthesis gasand reacting at least a portion the gas therein, and an expansionturbine fluidly coupled to the autothermal reformer for developingenergy with the gas from the autothermal reformer; and a synthesis unitfluidly coupled to the expansion turbine for receiving the synthesis gastherefrom and producing heavier hydrocarbons.

According to another aspect of the present invention, a method ofmanufacturing synthesis gas production system includes providing acompressor, fluidly coupling an autothermal reformer to the compressorfor producing synthesis gas and reacting at least a portion of the gastherein, and fluidly coupling an expansion turbine to the autothermalreformer for developing energy with the gas from the autothermalreformer.

A technical advantage of the present invention is that the system mayobtain higher production of synthesis gas by running all orsubstantially all of the compressed air from the gas turbine through theautothermal reformer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numbers indicate like features, and wherein:

FIG. 1 is a schematic representation of a process flow in which thepresent invention is well suited;

FIG. 2 is a schematic representation of a process flow showing aseparate syngas reactor and turbine; and

FIG. 3 is a schematic representation of a process flow showing anembodiment of the present invention with a combined syngas reactor andturbine;

FIG. 4 is a schematic representation of a process flow showing a secondembodiment of the present invention with a combined syngas reactor andturbine; and

FIG. 5 is a schematic representation of a process flow showing a thirdembodiment of the present invention with a combined syngas reactor andturbine.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiment of the present invention and its advantages arebest understood by referring to FIGS. 1-5 of the drawings, like numeralsbeing used for like and corresponding parts of the various drawings.

A. INTRODUCTION

The present invention involves the production of a synthesis gas, whichmay be used with synthesizing to produce methanol, DME, gasoline, ornumerous other substances. As noted in the background, the invention issuitable for use to produce syngas for a Fischer-Tropsch reactor,methanol reactor, ammonia reactor, or reactors requiring synthesis gas.The invention is presented, however, in context of the Fischer-Tropschprocess although it is to be understood that the application is muchbroader. A process flow in which the invention may be incorporatedincluding the use of a turbine is first presented in connection withFIGS. 1 and 2, and then a couple of specific embodiments of the presentinvention are described in connection with FIGS. 3-5.

B. THE CONVERSION OF HEAVIER HYDROCARBONS FROM GASEOUS LIGHTHYDROCARBONS

The present invention may be used in the conversion of lighterhydrocarbons to heavier hydrocarbons. Referring to FIG. 1, oneillustrative system for the conversion of heavier hydrocarbons fromgaseous light hydrocarbons is shown. A continuous stream of gaseouslight hydrocarbons, e.g., a natural gas stream, is conducted to a heatexchanger 10 of a conduit 12. While flowing through the heat exchanger10, the stream of light hydrocarbons is heated by exchange of heat witha process stream of generated synthesis gas which as will be describedbelow, comes from reactor 28. Typically, the feed stream of lighthydrocarbons is at a pressure in the range of from near atmosphericpressure to 600 psig and is preheated in the heat exchanger 10 to atemperature in the range of from about 500° F. to about 1000° F. Fromthe heat exchanger 10, the preheated feed stream is conducted by aconduit 14 to a synthesis gas generator, generally designated by thenumeral 16.

Air is drawn to an air compressor 18 by way of an inlet conduit 20, andfrom the compressor 18, a stream of air is conducted to a heat exchanger22 by a conduit 21. The stream of air is preheated in the heat exchanger22 to a temperature in the range of from about 500° F. to about 1000° F.by exchange of heat with the synthesis gas stream exiting the heatexchanger 10. From the heat exchanger 22, the preheated air is conductedto the synthesis gas generator 16 by a conduit 24.

While the synthesis gas generator 16 can take various forms, itgenerally includes a burner 26 connected to one end of a reactor vessel28. A bed of steam reforming catalyst 30, which typically containsnickel, is disposed within the reactor 28 at the end opposite the burner26.

In this embodiment, the reactor 28 is a refractory lined carbon steelvessel. Steam or water, which instantly converts to steam, is introducedinto the reactor 28 by way of a conduit 32 connected thereto, andoptionally carbon dioxide may be introduced into the reactor 28 by wayof a conduit 34 connected thereto.

In the operation of the synthesis gas generator 16, the preheated feedstream of gaseous light hydrocarbons from conduit 14 is intimately mixedwith a preheated stream of air from conduit 24 in the burner 26 andignited whereby the reaction takes place within the reactor 28. Thecombustion reaction is carried out at a temperature in the range of fromabout 1500° F. to about 2500° F. under sub-stoichiometric conditionswhereby the light hydrocarbons are partially oxidized. A gas streamincluding nitrogen, unreacted light hydrocarbons, hydrogen and carbonmonoxide is produced.

The unreacted light hydrocarbons in the combustion gas stream react withsteam introduced into the reactor 28 in the presence of the reformingcatalyst whereby additional hydrogen and carbon monoxide are producedtherefrom. Simultaneously, carbon dioxide may be introduced into thereactor 28 to react with unreacted light hydrocarbons to produceadditional carbon monoxide and hydrogen. The resulting synthesis gasstream generated within the generator 16 includes hydrogen, carbonmonoxide, carbon dioxide, nitrogen and unreacted light hydrocarbons,synthesis gas exits the reactor 28 by way of a conduit 36. Thecombustion and reforming reactions preferably occur as coexistingreactions that reach equilibrium in generator 16.

In order to control the ratio of hydrogen to carbon monoxide in thesynthesis gas stream produced in the synthesis gas generator 16 at aratio as close to 2:1 as possible, the rates of water introduced intothe reactor 28 by way of the conduit 32 and carbon dioxide introduced byway of the conduit 34 are varied. That is, the ratio of hydrogen tocarbon monoxide in the produced synthesis gas stream, or the compositionof the feed light hydrocarbon stream, or both, are monitored and used asthe basis for changing the flow rates of steam and carbon dioxide to thereactor 28 whereby a constant ratio of hydrogen to carbon monoxide atabout 2:1 is maintained in the existing synthesis gas.

The synthesis gas product stream produced in the generator 16 isconducted by the conduit 36 through the heat exchanger 10, then throughthe heat exchanger 22 and then to the inlet connection of a firsthydrocarbon synthesis reactor 38. Upon exiting the generator 16, thesynthesis gas is at a temperature in the range of from about 1000° F. toabout 2000° F. As the synthesis gas stream flows through the heatexchanger 10 on conduit 36 it gives up heat to the feed lighthydrocarbon stream. The light hydrocarbon stream in conduit 14 ispreheated to a temperature in the range of from about 500°0 F. to about1000° F. In a like manner, as the synthesis gas stream flows through theheat exchanger 22 on conduit 36, it gives up heat to the air flowing tothe generator 16 through conduit 24 whereby the air is also preheated toa temperature in the range of from about 500° F. to about 1000° F.Additional cooling of the synthesis gas stream is provided by a cooleror heat exchanger 23 disposed in the conduit 36 whereby the temperatureof the synthesis gas entering the reactor 38 is then in the range offrom about 350° F. to about 550° F.

In the hydrocarbon synthesis case, reactor 38 can take various forms,but in the embodiment shown is a tubular reactor containing a fixed bed37 of hydrocarbon synthesis catalyst. The catalyst of bed 37 may be ofcobalt supported on silica, alumina or silica-alumina material in anamount in the range of from about 5 to about 50 parts by weight ofcobalt per 100 parts by weight of the support material. The catalyst mayalso contain in the range of from about 0.05 to about 1 parts by weightof ruthenium per 100 parts by weight of support material as a promoter.

The synthesis gas stream flows into and through the reactor 38. The gasis delivered by conduit 36 and carried on its way by conduit 40. Asmentioned above, the temperature within the reactor 38 is in the rangeof from about 350° F. to about 550° F., and upon contact with thecatalyst, hydrogen and carbon monoxide in the synthesis gas stream reactto form heavier hydrocarbons and water.

The product stream produced in the reactor 38 exits the reactor by wayof a conduit 40 connected thereto. Conduit 40 leads the stream to acondenser 42. While flowing through the condenser 42, the heavierhydrocarbons and water contained in the stream are condensed. From thecondenser 42, a conduit 44 conducts the stream containing condensedcomponents to a separator 46 wherein the condensed heavier hydrocarbonsand water are separated and separately withdrawn. That is, the condensedwater is withdrawn from the separator 46 by way of a conduit 48connected thereto, and the condensed heavier hydrocarbons are withdrawnfrom the separator 46 by way of a conduit 50 connected thereto.

A residue gas stream from the separator 46 includes nitrogen andunreacted hydrogen, carbon monoxide, light hydrocarbons and carbondioxide. A conduit 52 connected to the separator 46 leads the residuegas stream from the separator 46 to a second hydrocarbon synthesisreactor 54 containing a fixed bed 56 of a hydrocarbon synthesiscatalyst, such as the one described above. The pressure and temperatureof the gas stream flowing through the reactor 54 are maintained atapproximately the same levels as the pressure and temperature within thereactor 38 by means of a heater or heat exchanger 58 disposed in theconduit 52 between the separator 46 and reactor 54. While flowingthrough the reactor 54, additional heavier hydrocarbons are formed fromhydrogen and carbon monoxide in the residue gas stream and the resultingproduct stream exits the reactor 54 by way of a conduit 60 connectedthereto. The conduit 60 leads the stream to a condenser 62 whereinheavier hydrocarbons and water contained therein are condensed. From thecondenser 62, the stream containing condensed components is conducted toa chiller 66 of a refrigeration unit by a conduit 64 wherein additionalhydrocarbons and water are condensed. The resulting stream is conductedfrom the chiller 66 to a separator 70 by a conduit 68 connectedtherebetween. Separator 70 will have water, heavier hydrocarbons, andresidue gas exit through three conduits.

Water is withdrawn from the separator 70 by a conduit 72 connectedthereto. The conduit 72 is in turn connected by way of conventionalvalves and controls (not shown) to the conduit 48, to a drain conduit 31and to the conduit 32 previously described whereby all or part of thecondensed water separated in the separators 46 and 70 is selectivelyconducted to the synthesis gas generator 16.

The condensed heavier hydrocarbons separated within the separator 70 arewithdrawn therefrom by a conduit 74 which connects to the conduit 50from the separator 46. The conduit 50 leads the heavier hydrocarbonsfrom both the separators 46 and 70 to a conventional fractionation unit76. A hydrocarbon product stream containing selected components iswithdrawn from the fractionation unit 76 by way of a conduit 78 whichconducts the product stream to storage or other location. Undesirablelight and heavy hydrocarbon fractions produced in the fractionation unit76 are withdrawn therefrom by conduits 80 and 82, respectively. Theconduits 80 and 82 connect to a conduit 84 which conducts theundesirable hydrocarbons to the inlet conduit 12 where they mix with thefeed stream of gaseous light hydrocarbons and are recycled.

The residue gas stream produced in the separator 70, which may includenitrogen and unreacted hydrogen, carbon monoxide, light hydrocarbons andcarbon dioxide, is withdrawn therefrom by a conduit 86 which leads theresidue gas stream to a catalytic combustor 88. The catalytic combustor88 may include a burner 90 into which the residue gas stream isconducted.

A stream of air is conducted to the burner 90 by a conduit 92 connectedto the discharge of an air blower 94. The residue gas stream from theseparator 70 and the air conducted to the burner 90 are intimately mixedtherein, ignited and discharged into a reactor 96 connected to theburner 90.

The reactor 96 contains a fixed bed of suitable nobel metal containingcatalyst 98, e.g., platinum or palladium, for promoting and catalyzingthe oxidation of the oxidizable components in the residue gas stream. Asa result of such oxidation an oxidation product stream including carbondioxide, water vapor and nitrogen is produced and withdrawn from thecombustor 88 by a conduit 100 connected thereto. The conduit 100optionally leads the product stream to a conventional carbon dioxideremoval unit 102. Carbon dioxide and water are removed from the streamby the carbon dioxide removal unit 102 thereby producing a relativelypure nitrogen product stream which is conducted from the unit 102 by aconduit 104 to a location of sale, storage or further processing.

The carbon dioxide removed by the unit 102 is withdrawn therefrom by aconduit 106 which leads the carbon dioxide to a compressor 108. Thedischarge of the compressor 108 is connected by way of conventionalvalves and controls (not shown) to a vent 35 and to the conduit 34previously described whereby all or part of the carbon dioxide isselectively introduced into the synthesis gas generator 16.

As previously described, the flow rates of the water conducted to thesynthesis gas generator 16 by way of the conduit 32 and carbon dioxideconducted thereto by way of the conduit 34 are varied as is necessary tocontrol the ratio of hydrogen to carbon monoxide in the synthesis gasstream produced to as close to 2:1 as possible. This in turn improvesthe efficiency of the hydrocarbon synthesis reactions carried out in thereactors 38 and 54. Further, the use of air, delivered by conduit 24, inthe synthesis gas generator 16 as the source of oxygen for the partialoxidation reaction carried out therein produces nitrogen in thesynthesis gas stream. Such nitrogen acts as a diluent in the hydrocarbonsynthesis reactors 38 and 54 and prevents hot spots on the catalyst andfurther increases the efficiency of the hydrocarbon synthesis reactions.The nitrogen together with the additional nitrogen produced in thecatalytic combustor 88, after carbon dioxide removal, form a relativelypure nitrogen product stream. In addition, the recycling of all or partof the optional carbon dioxide, which is transported in conduit 106provides additional carbon for producing heavier hydrocarbons andincreases overall process efficiency.

The system of FIG. 1 can include a gas turbine as will be furtherdescribed below in connection with FIG. 2. As an example of one way thesystem of FIG. 1 can be configured, catalytic combustor 88, the burner90, the blower 94, and air compressor 18 may be removed and replacedwith a gas turbine. The gas turbine could include a combustor to burnthe gas and the compressor section of the gas turbine could providecombustion air as blower 94 previously did and compressed air ascompressor 18 previously did. Other examples will be given furtherbelow.

Referring now to FIG. 2, another illustrative system 200 for theconversion of lighter hydrocarbons to heavier hydrocarbons is shown.System 200 combines a synthesis gas unit 202 with a synthesis unit 204and a gas turbine 206. System 200 uses gas turbine 206 to provide powerfor the process at a minimum, but is preferably designed to provide atleast some additional power.

Gas turbine 206 has a compressor section 208 and an expansion turbinesection 210. The power generated by the expansion turbine section 210drives the compressor section 208 by means of linkage 212, which may bea shaft, and any excess power beyond the requirements of compressorsection 208 may be used to generate electricity or drive other equipmentas figuratively shown by output 214. Compressor section 208 has inlet orconduit 216, where in the embodiment shown compressor 208 receives air.Compressor section 208 also has an outlet or conduit 218 for releasingcompressed air. Expansion turbine 210 has inlet or conduit 220 andoutlet or conduit 222. Outlet 218 of compressor section 208 providescompressed air to synthesis gas unit 202 through conduit 260.

Synthesis gas unit 202 may take a number of configurations, but in thespecific embodiment shown, includes syngas reactor 224, which as shownhere may be an autothermal reforming reactor. A stream of gaseous lighthydrocarbons, e.g., a natural gas stream, is delivered to syngas reactor224 by inlet or conduit 225. In some instances it may be desirable touse natural gas containing elevated levels of components, e.g., N₂, CO₂He, etc. that reduce the BTU value of the gas in conduit 225. Thesynthesis gas unit 202 may also include one or more heat exchangers 226,which in the embodiment shown is a cooler for reducing the temperatureof the synthesis gas exiting outlet 228 of syngas reactor 224. Heatexchanger 226 delivers its output to inlet 230 of separator 232.Separator 232 removes moisture which is delivered to outlet 234. It maybe desirable in some instances to introduce the water in conduit 234 assteam to expansion turbine 210. Synthesis gas exits separator 232through outlet or conduit 236. The synthesis gas exiting through outlet236 is delivered to synthesis unit 204.

Synthesis unit 204 may be used to synthesize a number of materials aspreviously mentioned, but in the specific example here is used tosynthesize heavier hydrocarbons as referenced in connection with FIG. 1.Synthesis unit 204 includes Fischer-Tropsch reactor 238, which containsan appropriate catalyst. The output of Fischer-Tropsch reactor 238 isdelivered to outlet 240 from which it travels to heat exchanger 242 andon to separator 244.

The product entering separator 244 is first delivered to inlet 246.Separator 244 distributes the heavier hydrocarbons separated therein tostorage tank or container 248 through outlet or conduit 250. Conduit 250may include additional components such as a conventional fractionationunit as shown in FIG. 1. Water withdrawn from separator 244 is deliveredto outlet or conduit 252. It may be desirable in some instances todeliver the water in conduit 252 as steam into expansion turbine 210.The residue gas from separator 244 exits through outlet or conduit 254.

System 200 includes a combustor 256. Combustor 256 receives air fromcompression section 208 delivered through conduit 258 which is fluidlyconnected to conduit 260 connecting outlet 218 with syngas reactor 224.The conduit 260 beyond the juncture with conduit 258 delivers bleed airto the autothermal reformer 224. Also, residue gas delivered byseparator 244 into conduit 254 is connected to combustor 256. Residuegas within conduit 254 is delivered to conduit 258 and then to combustor256. Intermediate conduit 260 and the connection of conduit 254 withconduit 258 may be a valve (not explicitly shown) for dropping thepressure delivered from compressor section 208 to combustor 256 in orderto match the pressure in conduit 254 as necessary. The output ofcombustor 256 is delivered to expansion turbine 210. In someembodiments, combustor 256 may be incorporated as part of gas turbine206 itself. Alternatively, the pressure in conduits 260 and 254 may beincreased by a compressor to match or exceed the pressure requirementsof combustor 256.

C. COMBINATION AUTOTHERMAL REFORMER AND TURBINE

Referring now to FIG. 3, there is shown a synthesis gas productionsystem 300 according to an aspect of the present invention has anautothermal-reformer-turbine unit 302. Synthesis gas production system300 may be included as part of system 304 for converting lighterhydrocarbons that further includes a synthesis unit 306.

Autothermal-reformer-turbine unit 302 includes an autothermal reformer(ATR) 308 and gas turbine 310. Gas turbine 310 includes a compressorsection 312 and an expansion turbine section 314. The power generated bythe expansion turbine section 314 drives the compressor section 312 bymeans of linkage 316, which may be a shaft. This embodiment preferablyhas an exact energy balance, but if excess energy is developed, it maybe removed from gas turbine 310 with an additional shaft extending fromexpansion section 314 as shown in FIG. 4. Compressor section 312 hasinlet or conduit 318, where compressor 312 receives air. Compressor 312also has an outlet or conduit 320 for releasing compressed air. Theexpansion turbine section 314 has inlet or conduit 322 and outlet orconduit 324. Outlet 324 of expansion section 314 provides compressedsynthesis gas into conduit 336.

Autothermal reformer 308 produces synthesis gas, but also serves as thecombustor of gas turbine 310. Compressor section 312 develops compressedair that is delivered to outlet 320, which is delivered to firstseparator 326, which will be described further below. After travelingthrough separator 326, compressed air is delivered by way of conduit 328to ATR 308. In addition, gaseous light hydrocarbons, such as naturalgas, are delivered to conduit 328 from conduit 330 and the residue gasis also delivered through conduit 332 into a portion of conduit 330 andthen to conduit 328 and ATR 308.

An issue in the performance of gas turbines is the balancing of theaxial loads on the shaft between the compressor section and theexpansion section. The present invention may realize the most efficientresults by the inclusion of thrust bearings in gas turbine 310 thatallow for a substantial imbalance between compressor section 312 andexpansion section 314. In order to use a preexisting turbine, however,unit 302 may provide for balancing of the loads within the turbinemanufacturer's specifications. This may be accomplished with firstseparator 326 or by bleeding air as will be described. The balancing,may be thought of as balancing the mass that is received in thecompressor section with the mass received by the turbine section or somepercentage thereof.

In the present invention, unit 302 receives additional mass fromconduits 330 and 332 between compressor section 312 and expansionsection 314 that would cause an imbalance without provisions being made.To address this, separator 326 may remove mass by separating outnitrogen or bleeding off a portion of the compressed air as suggested byFIG. 3. Separator 326 may include separation technology such as amembrane or carbon absorption or any other technique suitable for theremoval of nitrogen or other substances not needed by ATR 308. Inembodiments with sufficiently strong thrust bearings in compressor 312and turbine 314, no separator 326 or device for bleeding air isrequired.

ATR 308 will receive air and/or enriched air from conduit 328 along withthe gaseous light hydrocarbons and residual gasses from conduits 330 and332, respectively. ATR 308 will then autothermally reform the gas beforedelivering synthesis gas to conduit 334. The amount of gas delivered andproduced by ATR 308 may be notably higher than that which would normallybe expected from a normal gas-turbine combustor. ATR 308 does not fullycombust or react the gas, but because of the larger volumes of gasdelivered to ATR 308, an adequate amount of energy may be produced byexpansion section 314. The ATR 308 will have an exit temperature inconduit 304 within an acceptable range for input into expansion section314.

The gas delivered to ATR 308 may further be controlled to establish theproper ratios for ATR 308 such that the oxygen disappears and everythingsubstantially goes to CO or CO₂. To control the gas that is delivered toATR 308, one or more control valves, which are represented by controlvalve 331, may be used to control the ratio of gaseous lighthydrocarbons to air entering ATR 308.

Outlet 324 of expansion section 314 delivers its products to conduit 336which fluidly connects with heat exchanger or cooler 338. Then, theprocess continues from cooler 338 to conduit 340 and second separator342. The synthesis gas, which will contain some combustion productsand/or a nitrogen diluted gas, is delivered to expansion section 314 andexpanded before exiting outlet 324. Cooler 338 further cools the gaswhich will condense at least some water from the gas. In this example, aFischer-Tropsch process is presented, and the separator 342 will bedesirable. The water condensed by the gas as it travels through theexpansion section 314 and cooler 338, should be removed prior todelivering the product to second compressor 348. Thus, separator 342includes drain 344 for the removal of water. The gaseous product leavingseparator 342 is delivered by conduit 346 to compressor 348.

The syngas exiting expansion section 314 of gas turbine 310 may need tobe pressurized before entering the Fischer-Tropsch reactor 350, andthus, compressor 348 may be added. Separator 342 removed the liquidsthat may have condensed prior to the compressor 348. Compressor 348 maybe driven in a number of different ways. If the thrust bearings of gasturbine 310 allow for a sufficient imbalance for gas turbine 310 tocreate excess energy, a direct linkage 400 between expansion section 314and compressor 348 may be utilized as shown in FIG. 4. If excess energyis not available from gas turbine 310 in adequate quantities, the excessenergy may be used along with a supplement.

Compression in compressor 348 should adequately heat the gas existing toconduit 352 sufficiently for entry into Fischer-Tropsch reactor 350. Theinput to reactor 350 is preferably in the general range of 350° F. to500° F. In some situations, it may be desirable to add a heat exchangerbetween compressor 348 and Fischer-Tropsch reactor 350 to further heatthe gas therein.

Conduit 352 fluidly connects compressor 348 with reactor 350. Reactor350, for this example, may be a Fischer-Tropsch reactor which containsan appropriate catalyst. Other reactors may be used with other processesas previously noted. The output of Fischer-Tropsch's reactor 350 isdelivered to outlet 354 of conduit 356 connecting with heat exchanger358. After heat exchanger 358, the product is delivered via conduit 360to third separator 362. The heavier hydrocarbons separated in separator362 are then delivered to storage tank or container 364 by conduit 368.The residual gas is delivered to conduit 370. Separator 362 will alsoremove water which is delivered to conduit 372 for the case of aFischer-Tropsch process.

Conduit 370 delivers the residual gas to separator 374, which utilizes aseparation process such as a membrane or carbon absorption orcentrifugal process or other separation devices. For the instance of theFischer Tropsch example, nitrogen may be removed from the methane. Theoutput of separator 374 is delivered into conduit 332, which aspreviously noted delivers to ATR 308. In the preferred embodiment, theresidual gas is completely consumed back into ATR 308 since the energybalance of the system is zero, or even a slight amount of additionalenergy is needed for a second compressor 348.

Referring now to FIG. 5, there is shown another embodiment of thepresent invention. Fischer-Tropsch system 500 includes synthesis gasproduction system 501 and a Fischer-Tropsch reactor 550. In thisembodiment, compressed air is delivered through conduit 518 tocompressor 512. Compressor 512 delivers compressed air to conduit 520.Conduit 520 delivers compressed air to autothermal reformer 508. Gaseouslight hydrocarbons are delivered to conduit 520 and ultimately to ATR508 by conduit 530. Because the addition of mass to the flow betweencompressor 512 and turbine 514, the thrust bearings associated with link516 between compressor 512 and turbine 514 must be adequate to handlethe imbalance, or a sufficient amount of mass will need to be removed toallow the thrust bearings to be within their specifications for animbalance force. To remove the mass, if required, a separator removingnitrogen or a mechanism for bleeding a portion of the compressed air maybe installed on conduit 520 as shown by reference numeral 526. Thesynthesis gas exiting ATR 508 is delivered to turbine 514 by conduit534. The gas exiting turbine 514 enters conduit 536, which delivers itto Fischer-Tropsch's reactor 550. In this embodiment, the turbine maydecrease the pressure of a synthesis gas entering turbine 514 down to alesser, non-zero number as it exits into conduit 536. For example, itmay exit at 50 psi before being delivered to reactor 550. While a higherpressure may be desired for reactor 550, sufficiently active catalystsmay be utilized in reactor 550 such that the performance of reactor 550is adequate at the lower pressure. This system will obviate the need fora second compressor. Thus, while reactor 550 may not perform at optimumoutput, the reduced capital cost of removing a compressor may makeoperation in this mode desirable.

Although the present invention has been described in detail with respectto alternative embodiments, various changes and modifications may besuggested to one skilled in the art, and it should be understood thatvarious changes, substitutions and alterations can be made heretowithout departing from the spirit and scope of the invention as definedby the appended claims.

What is claimed is:
 1. A synthesis gas production system comprising:acompressor for compressing air or enriched air; an autothermal reformerfluidly coupled to the compressor and having a gaseous light hydrocarboninlet, the autothermal reformer for producing synthesis gas; anexpansion turbine section fluidly coupled to the autothermal reformerfor receiving synthesis gas from the autothermal reformer and developingenergy with synthesis gas from the autothermal reformer; and a separatorfluidly coupled between the compressor and autothermal reformer forremoving mass from the compressed air or enriched air flowingtherethrough.
 2. The system of claim 1 wherein the compressor andexpansion turbine comprise a single gas turbine.
 3. A method ofmanufacturing a synthesis gas production system comprising the stepsof:providing a compressor for compressing air or enriched air; providinga light hydrocarbon inlet; fluidly coupling an autothermal reformer tothe compressor and light hydrocarbon inlet, the autothermal reformerprovided for producing synthesis gas and reacting at least a portion ofthe synthesis gas in the autothermal reformer; and fluidly coupling anexpansion turbine section to the autothermal reformer for receivingsynthesis gas from the autothermal reformer and developing energy withthe synthesis gas from the autothermal reformer; and fluidly coupling aseparator between the compressor and autothermal reformer forselectively removing mass from the compressed air or enriched airflowing to the separator.
 4. The method of claim 3 wherein the step offluidly coupling a separator between the compressor and autothermalreformer for selectively removing mass comprises the step of fluidlycoupling a nitrogen separator between the autothermal reformer andcompressor for removing nitrogen from the compressed air or enriched airflowing through the separator.
 5. A synthesis gas production systemcomprising:a compressor for compressing air or enriched air; anautothermal reformer fluidly coupled to the compressor and having agaseous light hydrocarbon inlet, the autothermal reformer for producingsynthesis gas; an expansion turbine section fluidly coupled to theautothermal reformer for receiving synthesis gas from the autothermalreformer and developing energy with synthesis gas from the autothermalreformer; a separator fluidly coupled between the compressor andautothermal reformer for removing mass from the compressed air orenriched air flowing therethrough; and wherein the separator comprises anitrogen separator fluidly coupled to the compressor and autothermalreformer for removing nitrogen from the gas flow therethrough.